Recording medium and information storage apparatus

ABSTRACT

A recording medium and an information storage apparatus having high formatting efficiency are provided. The recording medium and the information storage apparatus give IDs for data to be stored. In one embodiment, one ID is provided for two data areas, and no two IDs are situated in line with each other on two adjacent tracks.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to recording media andinformation storage apparatuses, and, more particularly, to a recordingmedium and an information storage apparatus which allocate an ID to eachpiece of data and store information.

[0003] In recent years, there has been an increasing demand for largercapacity information storage apparatuses, as the amount of informationin the field of information processing has been increasing rapidly. In arecording medium, such as a magneto-optical disk, used in an informationstorage apparatus, information is recorded based on IDs. Because of thisID-based recording method, a larger recording capacity at higherrecording density requires a larger number of IDs, resulting in poorformatting efficiency.

[0004] In a magneto-optical disk, headers including IDs are formed bypits. A disk substrate is produced by an injection molding method usinga base plate. On the base plate, the pits are already formed by a photoprocessing technique. On the disk substrate, a recording layer and aprotection layer are formed to produce the magneto-optical disk. Thus,the pit size is determined by the wavelength of the laser beam.

[0005] In the magneto-optical disk, the mark size is reduced by the MSR(Magnetically induced Super Resolution) technology to a point where thepre-formatted pit size is twice or three times larger than the recordedmark size. As a result, the existence of the pits hinders theimprovement in recording density.

[0006] 2. Description of the Related Art

[0007]FIG. 1 shows an example format of a conventional magneto-opticaldisk.

[0008] A magneto-optical disk 1 of the prior art is rotated at aconstant rotational speed. The relative speed between a light beam andthe magneto-optical disk 1 on the inner peripheral side of themagneto-optical disk 1 is different from that on the outer peripheralside of the magneto-optical disk 1. Therefore, the magneto-optical disk1 is divided into four zones Z1 to Z4. The innermost zone Z1 has thelowest recording frequency among the four zones Z1 to Z4, and theoutermost zone Z4 has the highest recording frequency. This setting ofrecording frequencies is called a ZCAV (Zone Constant Angular Velocity)method, which is used to improve recording capacity.

[0009] In the magneto-optical disk 1, a header area 2 is formed in everysector having a predetermined length. A light beam is positioned to atarget sector in accordance with address (ID) information recorded inadvance on the corresponding header area 2 with a pit. A data area 3 inwhich information is to be stored is formed between every two headerareas 2.

[0010]FIG. 2 shows the data structure of an example data track of theconventional magneto-optical disk.

[0011] The data track is made up of a plurality of data sectors 4. Eachof the data sectors 4 includes a header 5 and a data field 6. An addressfor identifying each data field 6 is stored in each corresponding header5, and information is stored in each data field 6.

[0012] A buffer 7 is disposed between every two data sectors 4. A gap 8is formed between a header 5 and a data field 6. In each of the zones Z1to Z4, the headers 5 of two adjacent tracks are situated next to eachother. The data fields 6 of two adjacent tracks in the same zone arealso situated next to each other.

[0013]FIG. 3 shows the data structure of an example header of theconventional magneto-optical disk.

[0014] Each of the headers 5 comprises a sector mark 9, a first VFO(Variable Frequency Oscillator) synchronizing area 10, an address mark11, a first track address 12, a first sector address 13, a first errorcorrecting code 14, a second VFO synchronizing area 15, an address mark16, a second track address 17, a second sector address 18, a seconderror correcting code 19, and a postamble 20.

[0015] The sector mark 9 represents the start of a data sector 4. Thefirst VFO synchronizing area 10 initiates VFO synchronization forreading the first track address 12 and the first sector address 13. Thefirst address mark 11 represents the start of the first track address 12and the first sector address 13. The first track address 12 representsthe track address of scanned data. The first sector address 13represents the sector address of the scanned data. The first errorcorrecting code 14 is used to correct an error in the firsttrack-address 12 and the first sector address 13.

[0016] The second VFO synchronizing area 15 initiates VFOsynchronization for reading the second track address 17 and the secondsector address 18. The second address mark 16 represents the start ofthe track address 17 and the second sector address 18. The second trackaddress 17 represents the track address of scanned data. The secondsector address 18 represents the sector address of the scanned data. Thesecond error correcting code 19 is used to correct an error in thesecond track address 17 and the second sector address 18. The postamble20 represents the end of the header 5.

[0017] The position of a light beam is determined from either thecombination of the first track address 12 and the first sector address13 or the combination of the second track address 17 and the secondsector address 18.

[0018]FIG. 4 shows the data structure of an example data field of theconventional magneto-optical disk.

[0019] The data field 6 comprises a third VFO synchronizing-field 21, asynchronizing signal field 22, a data storage field 23, an errorcorrecting code field 24, and a postamble field 25.

[0020] The third VFO synchronizing area 21 initiates VFO synchronizationfor recording and reproducing data. The synchronizing signal field 22 issynchronizing with the data field 6, and initiates synchronization forreproducing data. The data storage field 23 stores data. The errorcorrecting code field 24 is used to detect and correct an error in thedata stored in the data storage field 23. The postamble field 25 isadded to reproduce the end of the data.

[0021] As explained above, the conventional magneto-optical disk 1 has aheader 5 in each data sector 4 to determine the position of a lightbeam.

[0022] However, despite the small size of marks formed by the MSRtechnology, the headers are formed by pits that are twice or three timeslarger than the marks, because the pits are read out without the MSRtechnology. The pit size is restricted to the size corresponding to thewavelength of the laser beam. If the data density is doubled or tripledby the MSR technology, a large proportion of the recording area isoccupied by the headers. As a whole, the recording density cannot beimproved due to the large-sized pits. Furthermore, since one header isprovided for each sector in the conventional magneto-optical disk, theformatting efficiency cannot be improved. Also, stagger caused inland/groove tracks reduces the formatting efficiency.

SUMMARY OF THE INVENTION

[0023] A general object of the present invention is to provide recordingmedia and information storage apparatuses in which the abovedisadvantages are eliminated.

[0024] A more specific object of the present invention is to provide arecording medium and an information storage apparatus which have higherrecording density with higher formatting efficiency.

[0025] The above objects of the present invention are achieved by arecording medium comprising: data sectors; and identifier portions eachprovided for more than one of the data sectors. The identifier portionsare arranged in positions shifted from each other on adjacent tracks.

[0026] Since only one identifier portion is provided for more than onedata sector in this recording medium, the formatting efficiency can beimproved. Also, when an identifier portion is being read from a track,an identifier portion on the adjacent tracks is not read. Thus, accuratedata access can be achieved. Furthermore, since the identifier portionsare shifted from each other on two adjacent tracks, the MSR(Magnetically induced Super Resolution) technique can be employed toreduce the mark size, and headers including the identifier portions canbe formed by pits, without reducing the recording density. As theheaders are not in line with each other on two adjacent tracks, theheaders can be wider than the tracks without adverse influence on eachother. Thus, the recording density can be improved even with the use ofpits.

[0027] The above objects of the present invention are also achieved byan information storage apparatus for making access to a recording mediumwhich has data sectors, and identifier portions each provided for morethan one data sectors, each of the identifier portions being arranged inpositions shifted from each other on adjacent tracks. This informationstorage apparatus comprises an address determination unit whichgenerates addresses of the data sectors based on the identifierportions, and determines whether a desired data sector is reached inaccordance with the addresses.

[0028] Since only one identifier portion is provided for more than onedata sector in this information storage apparatus, the formattingefficiency can be improved. Also, when an identifier portion is beingread from a track, an identifier portion on the adjacent tracks is notread. Thus, accurate data access can be achieved.

[0029] The above and other objects and features of the present inventionwill become more apparent from the following description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 shows an example disk format of a conventionalmagneto-optical disk;

[0031]FIG. 2 shows the structure of an example data area of theconventional magneto-optical disk;

[0032]FIG. 3 shows the structure of an example header of theconventional magneto-optical disk;

[0033]FIG. 4 shows the structure of an example data field of theconventional magneto-optical disk;

[0034]FIG. 5 shows a format of a first embodiment of a recording mediumin accordance with the present invention;

[0035]FIG. 6 shows a format of a data area of the first embodiment ofthe recording medium in accordance with the present invention;

[0036]FIG. 7 shows an example of address setting for data fields in thefirst embodiment of the recording medium in accordance with the presentinvention;

[0037]FIG. 8 shows another example of address setting for the datafields in the first embodiment of the recording medium in accordancewith the present invention;

[0038]FIG. 9 shows a format of a data area in a second embodiment of therecording medium in accordance with the present invention;

[0039]FIGS. 10A and 10B show the data structure of a sector mark in thesecond embodiment of the recording medium in accordance with the presentinvention;

[0040]FIG. 11 shows a format of a data area in a third embodiment of therecording medium in accordance with the present invention;

[0041]FIG. 12 shows a format of a data area in a fourth embodiment ofthe recording medium in accordance with the present invention;

[0042]FIG. 13 shows the relationship between a light beam and sectormarks in the fourth embodiment of the recording medium in accordancewith the present invention;

[0043]FIG. 14 is a block diagram of one embodiment of an informationstorage apparatus in accordance with the present invention;

[0044]FIG. 15 is a block diagram of a servo error detecting circuit ofthe information storage apparatus in accordance with the presentinvention;

[0045]FIG. 16 is a block diagram of an ODC of the information storageapparatus in accordance with the present invention;

[0046]FIG. 17 is a block diagram of a byte counter of the informationstorage apparatus in accordance with the present invention;

[0047]FIG. 18 shows the procedures for generating an event in theinformation storage apparatus in accordance with the present invention;

[0048]FIGS. 19A to 19F show an ID readout operation at a time of landtrack access in the information storage apparatus in accordance with thepresent invention;

[0049]FIG. 20 is an equivalent circuit for generating a sector markdetecting window of the information storage apparatus in accordance withthe present invention;

[0050]FIG. 21A to 21F show a process for generating a compound sectormark in the information storage apparatus in accordance with the presentinvention;

[0051]FIG. 22 is an equivalent circuit for generating a compound sectormark in the information storage apparatus in accordance with the presentinvention;

[0052]FIG. 23 is an equivalent circuit for correcting a sector markdetection pulse in the information storage apparatus in accordance withthe present invention;

[0053]FIG. 24 is an equivalent circuit of a gate pulse generator of theinformation storage apparatus in accordance with the present invention;

[0054]FIG. 25A to 25M illustrate an operation of the gate pulsegenerator of the information storage apparatus in accordance with thepresent invention;

[0055]FIG. 26A to 26D illustrate a read/write start timing operation ina data area of the information storage apparatus in accordance with thepresent invention;

[0056]FIG. 27A to 27C illustrate the state of a servo error detectionsensitivity of the information storage apparatus in accordance with thepresent invention;

[0057]FIG. 28 shows a format in a fifth embodiment of the recordingmedium in accordance with the present invention; and

[0058]FIG. 29 shows a format in a sixth embodiment of the recordingmedium in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059] The following is a description of embodiments of the presentinvention, with reference to the accompanying drawings.

[0060]FIG. 5 shows a format in a first embodiment of a recording mediumin accordance with the present invention. In this figure, the samecomponents as in FIG. 1 are denoted by the same reference numerals.

[0061] In a magneto-optical disk 100 of this embodiment, data areas 101and headers 102 have different formats from the data areas 3 and theheaders 5.

[0062]FIG. 6 shows a format of a data area in the first embodiment ofthe recording medium. It should be understood that FIG. 6 does not showthe actual physical positions of headers and data fields.

[0063] In the magneto-optical disk 100 of this embodiment, tracks Tr1 toTrn adjacent to one another are defined by grooves. The tracks Tr1, Tr3,. . . are the grooves etched in the substrate of the magneto-opticaldisk 100. On each of the tracks Tr1, Tr3, . . . , one header 102 isfollowed by two data fields 103-1 and 103-2.

[0064] The tracks Tr2, Tr4, . . . are formed in lands between thegrooves-formed on the substrate of the magneto-optical disk 100. On eachof the tracks Tr2, Tr4, . . . , one header 104 is followed by two datafields 105-1 and 105-2.

[0065] The headers 102 of the tracks Tr1, Tr3, . . . formed in thegrooves are aligned in the radial direction of the magneto-optical disk100 (i.e., in the direction of an arrow A). The headers 104 of thetracks Tr2, Tr4, . . . formed in the lands are also aligned in theradial direction of the magneto-optical disk 100 (i.e., in the directionof the arrow A).

[0066] The data fields 103-1 of the tracks Tr1, Tr3, . . . formed in thegrooves and the data fields 105-2 of the tracks Tr2, Tr4, . . . formedin the lands are aligned in the radial direction of the magneto-opticaldisk 100 (i.e., in the direction of the arrow A). The data fields 103-2of the tracks Tr1, Tr3, . . . formed in the grooves and the data fields105-1 of the tracks Tr2, Tr4, . . . formed in the lands are also alignedin the radial direction of the magneto-optical disk 100 (i.e., in thedirection of the arrow A).

[0067] While the headers 102 of the tracks Tr1, Tr3, . . . are scanned,for instance, the headers 104 of the adjacent tracks Tr2, Tr4, . . . arenever simultaneously scanned. Thus, wrong ID detection can be prevented.Especially when a high-density recording technique, such as the MSR(Magnetic Super Resolution) technique, is employed, the adjacent headersnever overlap with each other, because marks are smaller than pits.Thus, the track density can be improved. Furthermore, each two datafields require only one header, for instance, each header 102 for eachtwo data fields 103-1 and 103-2, and each header 104 for each two datafields 105-1 and 105-2. In this arrangement, the number of headersformed on the magneto-optical disk 100 can be reduced. Thus, theformatting efficiency on the magneto-optical disk 100 can be improved.

[0068] The structure of each header 102 is the same as the header 5shown in FIG. 3. Likewise, the structure of each of the data fields103-1, 103-2, 105-1, and 105-2 is the same as the data field 6 shown inFIG. 4.

[0069] Since only one header is set for each two data fields, it isnecessary to generate two addresses from an address obtained from eachheader.

[0070]FIG. 7 shows an example of address setting for the data fields inthe first embodiment of the recording medium in accordance with thepresent invention. In this figure, more specific reference numerals 102a, 102 b, 102 c, . . . are allocated to the headers 102, and referencenumerals 103-1 a and 103-2 a, 103-1 b and 103-2 b, . . . are allocatedto the data fields 103-1 and 103-2.

[0071] As shown in FIG. 7, the address of the header 102 a on the trackTr1 is “N”, the address of the data field 103-1 a is “N”, and theaddress of the data field 103-2 a is “N+1”. The address of the nextheader 102 b is “N+2”, the address of the data field 103-1 b is “N+2”,and the address of the data field 103-2 b is “N+3”. The addresses of thedata fields 103-2 a and 103-2 b are determined by adding “1” to theaddresses “N” and “N+2” of the headers 102 a and 102 b, respectively, inaccordance with a passing signal of one sector.

[0072] In the above manner, addresses can be continuously allocated toall the data fields. It should be understood that the above manner ofaddress setting can be applied to the headers 104 and the data fields105-1 and 105-2.

[0073] In this embodiment, even if the marks on the magneto-optical diskare formed by the MSR technique so as to dramatically reduce the widthsof the marks, the headers 102 and 104 formed by pits never overlap witheach other. Accordingly, the headers 102 and 104 wider than therespective tracks never have adverse effects on each other. Thus, therecording density can be dramatically increased.

[0074] Although the headers 102 and 104 are formed on lands and grooves,they can be formed on lands only. The formation of the headers 102 and104 is not limited to the above examples, but other techniques can beemployed to form the headers 102 and 104.

[0075] In the example shown in FIG. 7, the addresses of the headers 102are not consecutive. However, it is also possible to allocateconsecutive addresses to the headers 102. In such a case, the addressesof the data fields 103-1 and 103-2 are determined in compliance with theaddresses of the headers 102.

[0076]FIG. 8 shows another example of address setting for the datafields in the first embodiment of the recording medium in accordancewith the present invention. In this figure, the same reference numeralsas in FIG. 7 are allocated to the headers 102 and the data fields 103-1and 103-2.

[0077] As shown in FIG. 8, the address of the header 102 a is “N”, andthe address of the next header 102 b is “N+1”. The address of the datafield 103-1 a that immediately follows the header 102 a is “2N”, and theaddress of the data field 103-2 a that follows the data field 103-1 a is“2N+1”. The address of the data field 103-1 b that immediately followsthe header 102 b is “2(N+1)”, and the address of the data field 103-2 bthat follows the data field 103-1 b is “2(N+1)+1”.

[0078] In this modification, consecutive addresses can be allocated tothe headers 102. It should be understood that the above manner ofaddress setting can be applied to the headers 104 and the data fields105-1 and 105-2.

[0079] In the first embodiment, one header is set for each two datafields. However, it is also possible to put a sector mark between thedata fields 103-1 and 103-2, for instance. With sector marks, the startof each sector can be accurately identified. Since the sector marks areidentical and arranged in line across the adjacent tracks, regardless ofthe addresses, they can be accurately detected even if crosstalk occurs.

[0080]FIG. 9 shows a format of a data area in a second embodiment of therecording medium in accordance with the present invention. In thisfigure, the same components as in FIG. 6 are denoted by the samereference numerals.

[0081] A data area 110 of this embodiment has a sector mark 111 betweeneach two data fields 103-1 and 103-2, and between each two data fields105-1 and 105-2. The sector mark 111 is identical to the sector mark 9shown in FIG. 3.

[0082]FIG. 10A shows the data structure of a sector mark having a firstpattern, and FIG. 10 B shows the data structure of a sector mark havinga second pattern. The first and second patterns shown in FIGS. 10A and10B are the “ODD BAND” and the “EVEN BAND”, respectively, specified inISO/IEC 15041.

[0083] Either of the two patterns shown in FIGS. 10A and 10B is used foreach sector mark 111. As the first pattern is the “ODD BAND” specifiedin ISO/IEC 15041, a sector mark 111 having the first pattern has three6-cycle “6T” no-mark portions and three 12-cycle “12T” mark portionsalternately, and two 12-cycle “12T”no-mark portions and two 6-cycle “6T”mark portions alternately, as shown in FIG. 10A. A bit pattern“0001”+“01” is added at the end of the first pattern.

[0084] The second pattern is the “EVEN BAND” specified in ISO/IEC 15041.A sector mark 111 having the second pattern has three 6-cycle “6T”markportions and three 12-cycle “12T” no-mark portions alternately, and thentwo 12-cycle “12T” mark portions and two 6-cycle “6T” no-mark portionsalternately, as shown in FIG. 10B. A bit pattern “000001” is added atthe end of the second pattern.

[0085] The sector marks 111 are aligned with the sector marks 9 of theheaders 102 and 104 on the adjacent tracks in the direction of the arrowA, i.e., in the radial direction of the magneto-optical disk 100. Thesector marks 111 are put between the data fields 103-1 and 103-2, andbetween the data fields 105-1 and 105-2, so as to initiatesynchronization to compensate window shifts caused by disk displacementor rotation jitter.

[0086] Although the sector marks 111 between the data fields 103-1 and103-2 and between the data fields 105-1 and 105-2 are identical to thesector marks 9 in the headers 102 and 104 in this embodiment, the sectormarks 111 may have different patterns from the sector marks 9. Also, thesector marks 111 are situated in line with the sector marks 9 of theadjacent headers 102 and 104. However, the sector marks 111 may beslightly deviated from the line of the sector marks 9 of the headers 102and 104, so that the sector marks 111 do not overlap with the headers102 and 104 in the radial direction. In this arrangement, the pitsforming the headers 102 and 104 and the sector marks 111 can expand intothe adjacent tracks. Thus, the track pitch can be made narrower than thediameter of a laser beam for forming the pits.

[0087]FIG. 11 shows a format of a data area in a third embodiment of therecording medium in accordance with the present invention. In thisfigure, the same components as in FIG. 9 are denoted by the samereference numerals.

[0088] A data area 120 of this embodiment has a sector mark 123 in eachheader 121, a sector mark 124 in each header 122, a sector mark 125between each two data fields 103-1 and 103-2, and a sector mark 126between each two data fields 105-1 and 105-2. Each of the sector marks123 and 126 has the first pattern shown in FIG. 10A, while each of thesector marks 124 and 125 has the second pattern shown in FIG. 10B.

[0089] As each of the sector marks 123 has the first pattern while eachof the sector marks 124 has the second pattern in this embodiment, thesector marks can be distinguished between sectors having IDs and sectorshaving no IDs, and the sectors having IDs can be identified from theland and groove arrangements.

[0090] The sector marks are formed both in the lands and the grooves inthis embodiment. In a land/groove medium having a track pitch smallerthan the diameter of a beam, however, it is possible to form the sectormarks either in the lands or the grooves and detect the sector marksboth in the lands and the grooves from crosstalk.

[0091]FIG. 12 shows a format of a data area in a fourth embodiment ofthe recording medium in accordance with the present invention. In thisfigure, the same components as in FIG. 11 are denoted by the samereference numerals.

[0092] A data area 130 of this embodiment does not have the sector marks124 and 126 of the third embodiment on the tracks Tr2 and Tr4. Thesector marks 123 are of course detected at a time of groove trackscanning. In this embodiment, the sector marks 123 are also detected bymeans of crosstalk at a time of land track scanning.

[0093]FIG. 13 shows the size relationship between a light beam andsector marks of the fourth embodiment of the recording medium inaccordance with the present invention.

[0094] In FIG. 13, sector marks are formed on the groove tracks Tr1 andTr3, and no sector marks are formed on the land tracks Tr2 and Tr4. Whena laser beam L scans the land track Tr2, the land track Tr2 comes in thecenter of the laser beam L, as shown in FIG. 13. Although no sectormarks are formed on the land track Tr2, the laser beam L that is largerthan the track pitch scans parts of the sector marks formed on the twoadjacent groove tracks Tr1 and Tr3, thereby detecting the sector marksby means of crosstalk.

[0095] In accordance with this embodiment, the MSR (Magnetic SuperResolution) technique can be employed to reduce the mark size, andheaders including the identifier portions can be formed by pits, withoutreducing the recording density. As the headers are not in line with eachother on two adjacent tracks, the headers can be wider than the trackswithout adverse influence to each other. Thus, the recording density canbe increased even with the large pits.

[0096] Although a magneto-optical disk is employed as the recordingmedium in the above embodiments, the application of the presentinvention is not limited to magneto-optical disks. For instance, theabove embodiments are applicable to a recording medium on whichrecording is performed by a MAMMOS technique or the like for formingmarks narrower than the diameter of a laser beam.

[0097]FIG. 14 is a block diagram of one embodiment of an informationstorage apparatus in accordance with the present invention.

[0098] A magneto-optical disk device 200 of this embodiment storesinformation in the magneto-optical disk shown in FIGS. 5 to 13. Themagneto-optical disk device 200 comprises a magneto-optical disk 201, aspindle motor 202, a magnetic head 203, a magnetic head control circuit204, an optical head 205, a positioner 206, an LD control circuit 207, ahead amplifier 208, a read circuit 209, a servo circuit 210, a servoerror detecting circuit 211, and an ODC (Optical Disk Controller) 212.

[0099] The magneto-optical disk 201 has any of the formats shown inFIGS. 5 to 13. The magneto-optical disk 201 is rotated by the spindlemotor 202 in a direction indicated by an arrow C. The magnetic head 203is placed on a surface of the magneto-optical disk 201 in the radialdirection (in a direction indicated by an arrow B). The magnetic head203 applies a magnetic field to the magneto-optical disk 201 to recordand reproduce information thereon.

[0100] The optical head 205 is placed on the other surface of themagneto-optical disk 102. The optical head 205 emits a light beam L ontothe magneto-optical disk 201. The optical head 205 is engaged with thepositioner 206, and can be moved by the positioner 206 in the radialdirection of the magneto-optical disk 201 (in the direction indicated bythe arrow B). The optical head 205 is connected to the LD controlcircuit 207, and is driven in accordance with a signal supplied from theLD control circuit 207.

[0101] The light beam L is reflected by the magneto-optical disk 201,and returned to the optical head 205. The reflected light from themagneto-optical disk 201 is then converted into reproduction signalswhich are supplied to the head amplifier 208. The head amplifier 208separates a tracking error signal TES, ID and sector mark signals, andan information signal MO from the reproduction signals. The ID andsector mark signals and the information signal MO separated by the headamplifier 208 are sent to the read circuit 209. The read circuit 209separates the ID and sector mark signals from the information signal MO,and demodulates the ID and sector mark signals as well as theinformation signal MO.

[0102] The ID-signal, the sector mark signal SM, and the informationsignal MO demodulated by the read circuit 209 are then sent to the ODC212. In accordance with the ID signal and the sector mark signal SM, theODC 212 determines the illumination position of the light beam on themagneto-optical disk 201, and generates a sensitivity switching signalfor switching the servo sensitivity. The ODC 212 also sends theinformation signal MO to a host computer.

[0103] The sensitivity switching signal generated from the ODC 212 issupplied to the servo error detecting circuit 211. In accordance withthe sensitivity switching signal, the servo error detecting circuit 211controls the sensitivity for detecting a servo error from the trackingerror signal TES supplied from the head amplifier 208. When the trackingerror signal TES supplied from the head amplifier 208 is larger than athreshold value set by the sensitivity switching signal supplied fromthe ODC 212, the servo error detecting circuit 211 determines that thereis a servo error, and outputs a high-level signal.

[0104] The detection result of the servo error detecting circuit 211 issupplied to the ODC 212 and the servo circuit 210. When the servo errordetecting circuit 211 detects a servo error, the ODC 212 stops writingand reading operations, and the servo circuit 210 stops theservomechanism.

[0105]FIG. 15 is a block diagram of the servo error detecting circuit ofthe embodiment of the information storage apparatus in accordance withthe present invention.

[0106] The servo error detecting circuit 211 comprises a switch 213,comparators 214 and 215, an OR gate 216, and resistors R1 to R4. Theresistors R1 to R3 are connected in series between a voltage +V and avoltage −V of a power source. A first threshold value is generated atthe connection point between the resistors R1 and R2, and a secondthreshold value is generated at the connection point between theresistors R2 and R3.

[0107] A series circuit made up of the switch 213 and the resistor R4 isconnected to the resistor R2 in parallel. The connection of the resistorR4 to the resistor R2 is switched by switching on and off the switch213. The switch 213 is connected to the ODC 212, and switches theconnection of the resistor R4 to the resistor R2 in accordance with thesensitivity switching signal supplied from the ODC 212. When thesensitivity switching signal supplied from the ODC 212 is high, i.e.,when high sensitivity is required, the switch 213 is switched on toconnect the resistor R4 to the resistor R2 in parallel. When theresistor R4 and the resistor R2 are connected in parallel, the resistorR4 lowers the resistivity between the resistor R1 and the resistor R3.Accordingly, the difference between the first threshold value and thesecond threshold value becomes smaller, and the sensitivity becomeshigher. When the sensitivity switching signal supplied from the ODC 212,i.e., when low sensitivity is required, the switch 213 is switched offto leave only the resistor R2 between the resistor R1 and the resistorR3. With only the resistor R2 being connected between the resistor R1and the resistor R3, the resistivity between the resistor R1 and theresistor R3 becomes higher. Accordingly, the difference between thefirst threshold value and the second threshold value becomes larger, andthe sensitivity becomes lower.

[0108] The first threshold value outputted from the connection pointbetween the resistor R1 and the resistor R2 is supplied to the invertinginput terminal of the comparator 214. The second threshold valueoutputted from the connection point between the resistor R2 and theresistor R3 is supplied to the non-inverting input terminal of thecomparator 215.

[0109] The servo error signal TES outputted from the head amplifier 208is supplied to the non-inverting input terminal of the comparator 214.The comparator 214 compares the servo error signal TES with the firstthreshold value. When the servo error signal TES is smaller than thefirst threshold value, the output of the comparator 214 is low. When theservo error signal TES is larger than the first threshold value, theoutput of the comparator 214 is high.

[0110] The servo error signal TES outputted from the head amplifier 208is also supplied to the inverting input terminal of the comparator 215.The comparator 215 compares the servo error signal TES with the secondthreshold value. When the servo error signal TES is larger than thesecond threshold value, the output of the comparator 215 is low. Whenthe servo error signal TES is smaller than the second threshold value,the output of the comparator 215 is high.

[0111] The outputs of the comparators 214 and 215 are supplied to the ORgate 216. The OR gate 216 outputs the OR logic between the outputs ofthe comparators 214 and 215. The output of the OR gate 216 is suppliedas the output of the servo error detecting circuit 211 to the ODC 212and the servo circuit 210.

[0112] The ODC 212 detects the address from a header on themagneto-optical disk 201, and counts the number of data fields that havepassed. In accordance with the detected address from the header and thenumber of data fields that have passed, the ODC 212 identifies theaddress of a data field without a header, and then reads or writes. Forinstance, the ODC 212 adds the number of data fields that have passed tothe detected address so as to determine the address of the data fieldwithout a header.

[0113]FIG. 16 is a block diagram of the ODC of the embodiment of theinformation storage apparatus in accordance with the present invention.

[0114] The ODC 212 comprises a sector mark detector 217, an ID detector218, a byte counter 219, an address counter 220, comparators 221, 222,and 223, a gate pulse generator 224, a controller 225, and registers 226and 227.

[0115] The sector mark detector 217 detects a sector mark signal SMsupplied from the read circuit 209, and sends a sector marksynchronizing signal in synchronization with the sector mark signal SMto the byte counter 219. The ID detector 218 detects an ID address fromthe ID signal supplied from the read circuit 209, and sends the IDaddress to the comparator 221. The ID detector 218 also sends an IDsynchronizing signal in synchronization with the ID signal to the bytecounter 219. When the ID address is not detected, the ID detector 218sends an ID detection failure notification to the gate pulse generator224.

[0116] The byte counter 219 counts in accordance with a synchronizingevent, and outputs a signal corresponding to the selected synchronizingevent. More specifically, the byte counter 219 counts the sector marksynchronizing signal supplied from the sector mark detector 217 and theID synchronizing signal supplied from the ID detector 218 assynchronizing events. In accordance with the count result, the bytecounter 219 supplies a sector mark detecting window to the sector markdetector 217, and an ID detecting window to the ID detector 218.

[0117] The byte counter 219 also detects each sector that has passed,based on the count result. A 1-sector pass notification is supplied tothe address counter 220 every time one sector passes. The addresscounter 220 counts the 1-sector pass notifications supplied from thebyte counter 219, and generates an extrapolated address from the IDaddress of a sector without an ID address. The extrapolated addressgenerated by the address counter 220 is supplied to the comparators 221,22, and 223.

[0118] The comparator 221 compares the ID address supplied from the IDdetector 218 with the extrapolated address supplied from the addresscounter 220, and outputs a signal in accordance with the comparisonresult. When the ID address is not identical with the extrapolatedaddress, the output signal of the comparator 221 is high. When the IDaddress is identical with the extrapolated address, the output signal ofthe comparator 221 is low. The output signal of the comparator 221 issupplied to the gate pulse generator 224.

[0119] The comparator 222 compares the extrapolated address suppliedfrom the address counter 220 with a process start sector address storedin the register 226, and outputs a signal in accordance with thecomparison result. When the extrapolated address supplied from theaddress counter 220 is identical with the process start sector addresssupplied from the register 226, the output signal of the comparator 222is high. When the extrapolated address supplied from the address counter220 is not identical with the process start sector address supplied fromthe register 226, the output signal of the comparator 222 is low. Theoutput signal of the comparator 222 is supplied to the gate pulsegenerator 224. In accordance with the output signal, the gate pulsegenerator 224 detects a process start position.

[0120] The comparator 223 compares the extrapolated address suppliedfrom the address counter 220 with a process end sector address stored inthe register 227, and outputs a signal in accordance with the comparisonresult. When the extrapolated address supplied from the address counter220 is identical with the process end sector address supplied from theregister 227, the output signal of the comparator 223 is high. When theextrapolated address supplied from the address counter 220 is notidentical with the process end sector address supplied from the register227, the output signal of the comparator 223 is low. The output signalof the comparator 223 is supplied to the gate pulse generator 224. Inaccordance with the output signal, the gate pulse generator 224 detectsa process end position.

[0121] The register 226 is connected to the controller 225. Thecontroller 225 supplies the process start address to the register 226.The register 227 is also connected to the controller 225. The controller225 supplies the process end address to the register 227.

[0122] The gate pulse generator 224 generates a write gate pulse, a readgate pulse, and a servo sensitivity switching signal, based on the countvalue supplied from the byte counter 219, and on the process startaddress and the process end address supplied from the comparators 222and 223, respectively. If the ID detection failure notification issupplied from the ID detector 218 to the gate pulse generator 224, thegate pulse generator 224 stops the gate pulse generating operation.

[0123]FIG. 17 is a block diagram of the byte counter of the embodimentof the information storage apparatus in accordance with the presentinvention.

[0124] The byte counter 219 comprises registers 228 and 229, amultiplexer 230, an OR gate 231, a counter 232, and comparators 233-1 to233-n.

[0125] The register 228 holds synchronizing values as timing values forgenerating synchronizing events. The synchronizing values stored in theregister 228 are supplied to the multiplexer 230. The multiplexer 230receives a synchronizing event as well as the synchronizing values fromthe register 228. The synchronizing event is a signal which is high whenthe read gate pulse, the write gate pulse, or the servo sensitivitypulse switching signal is generated, and which is low when the pulsegenerating operation is stopped.

[0126] The multiplexer 230 selects a desired synchronizing value fromthe register 228 in accordance with the supplied synchronizing event,and sends the selected synchronizing value to the counter 232. Thesynchronizing event is also supplied to the OR gate 231, which generatesthe OR logic of the synchronizing event. The output of the OR gate 231is supplied to the counter 232. The counter 232 starts counting from thesynchronizing value selected by the multiplexer 230. The count value ofthe counter 232 is supplied to the comparators 233-1 to 233-n.

[0127] Each of the comparator 233-1 to 233-n receives the count valuefrom the counter 232 and a timing value from the register 229. Thetiming values, each of which represents the count value for generatingeach synchronizing event, are stored in the register 229 in advance.

[0128] Each of the comparators 233-1 to 233-n compares the count valuefrom the counter 232 with the timing value from the register 229, andoutputs a signal in accordance with the comparison result. When thecount value from the counter 232 is identical with the timing value fromthe register 229, the output signal of each of the comparators 233-1 to233-n is high. When the count value from the counter 232 is notidentical with the timing value from the register 229, the output signalof each of the comparators 233-1 to 233-n is low.

[0129] In the above manner, each of the comparators 233-1 to 233-noutputs a signal that is high when an event should be generated. Theoutputs of the comparators 233-1 to 233-n are supplied to the sectormark detector 217, the ID detector 218, the address counter 220, and thegate pulse generator 224.

[0130]FIG. 18 shows the procedures for generating an event in theembodiment of the information storage apparatus in accordance with thepresent invention. The event explained with reference to FIG. 18 is aninformation read event.

[0131] First, as the light beam reaches a position in which a sectormark is recorded, the ODC 212 opens the sector mark detecting window instep S1-1. With the sector mark detecting window being open, the sectormark becomes detectable. If the sector mark signal is in synchronizationwith the sector mark detecting window here, the sector mark can be readin step S1-2. The sector mark detecting window is then closed in stepS1-3. Here, the period of the sector mark detecting window is longerthan the period of the sector mark. For instance, if the period of thesector mark is 5 bytes, the period of the sector mark detecting windowis 8 bytes, being expanded by 3 bytes before and after the sector mark.Thus, the servo mark is situated within the servo mark detecting window,and accurate detection of the sector mark is ensured.

[0132] After the sector mark detecting window is closed in the stepS1-3, the ID detecting window is opened in step S1-4. With the IDdetecting window being open, an ID becomes detectable. If the ID signalis in synchronization with the ID detecting window here, the ID can beread in step S1-5. The justification of the ID detection is determinedby a CRC (cyclic redundancy check) attached to each ID. If the ID isdetected and the CRC attached to the ID is determined to be normal, theID detecting window is closed in step S1-6. Here, the period of the IDdetecting window is longer than the period of ID.

[0133] After the ID detecting window is closed, whether the detected IDbelongs to a land or a groove is determined in step S1-7.

[0134] Next, the servo error detection sensitivity is increased in step1-8, and a read gate is opened in step S1-9. A synchronizing signaldetecting window is then opened, and a synchronizing signal becomesdetectable in step S1-10. If the synchronizing signal is insynchronization with the synchronizing signal detecting window, thesynchronizing signal is read out in step S1-11. The synchronizing signaldetecting window is then closed in step S1-12. Here, the period of thesynchronizing signal detecting window is longer than the period of thesynchronizing signal.

[0135] After the synchronizing signal detecting window is closed, datais read out in step S1-13. After the data is read out, the read gate isclosed in step S1-14. The servo error detection sensitivity is thenreduced, and the servo is stabilized in step S1-15. Here, the read gateopen period is longer than the period of the read data. Thus, the dataof one sector has been read, and the light beam has passed the sector inthe S1-16.

[0136] When writing information, instead of reading it, the write gateis opened in the step S1-9, and is closed in the step S1-14. Thesynchronizing signal detection of the steps S1-10 to S1-12 is skipped.The write gate open period is also longer than the period of the writtendata.

[0137] In the above manner, read and write cycles are performed on thetracks Tr1, Tr2, Tr3, Tr4, . . . In this embodiment, there are dataareas with no header. Therefore, it is necessary to prevent the ID readgate from being switched on in those data areas.

[0138]FIGS. 19A to 19F show an operation of the ODC in the embodiment ofthe information storage apparatus in accordance with the presentinvention. FIG. 19A shows the data format of a land, FIG. 19B shows thedata format of a groove, FIG. 19C shows a land sector mark detectionpulse, FIG. 19D shows a groove sector mark detection pulse, FIG. 19Eshows a sector mark detecting window, and FIG. 19F shows an ID readgate.

[0139] The magneto-optical disk 201 used in this embodiment has landsformatted as shown in FIG. 19A, and grooves formatted as shown in FIG.19B. In the magneto-optical disk 201, each land track is in very closeproximity with each adjacent groove track. Because of this, whenscanning a land track, a groove ID might be wrongly read out. Thisembodiment is to prevent such an error.

[0140] When searching for a sector mark on the land track shown in FIG.19A, sector marks detected from the groove track shown in FIG. 19Bshould be ignored. Therefore, when the sector mark detection is startedas shown in FIG. 19E, the sector mark detection pulse on the groovetrack shown in FIG. 19D is ignored. When a sector mark on the land trackis detected as shown in FIG. 19C, the sector mark detecting window isclosed as shown in FIG. 19E, and the ID read gate is opened as shown inFIG. 19F. Since the ID read gate is opened only when the sector mark ina header on the land track is detected, the ID read gate is neverwrongly opened when the sector mark in a header on the groove track isdetected. Thus, reading the ID on the groove track shown in FIG. 19B dueto crosstalk can be prevented.

[0141]FIG. 20 is an equivalent circuit of an operation of the ODC of theinformation storage apparatus in accordance with the present invention.The processes shown in FIGS. 19A to 19F are realized by the equivalentcircuit of FIG. 20.

[0142] As shown in FIG. 20, the equivalent circuit comprises AND gates234 and 235, a NOT circuit 236, an OR gate 237, and a sector markdetecting window output part 238.

[0143] The AND gate 234 receives a land sector mark detection pulse fromthe sector mark detector 217 and a land tracking signal from thecontroller 225. The AND gate 234 then determines the AND logic betweenthe land sector mark detection pulse and the land tracking signal. TheAND gate 235 receives a groove sector mark detection pulse from thesector mark detector 217 and the land tracking signal inverted by theNOT circuit 236. The AND gate 235 then determines the AND logic betweenthe groove sector mark detection pulse and the inverted land trackingsignal.

[0144] The outputs of the AND gates 234 and 235 are supplied to the ORgate 237, which determines the OR logic between the output of the ANDgate 234 and the output of the AND gate 235. The output of the OR gate237 is supplied to the sector mark detecting window output part 238. Inaccordance with the signal supplied from the OR gate 237, the sectormark detecting window output part 238 closes the sector mark detectingwindow. Meanwhile, the sector mark detecting window output part 238receives a sector mark search start pulse generated as an event insidethe byte counter 219. In accordance with the sector mark search startpulse, the sector mark detecting window output part 238 opens the sectormark detecting window. In accordance with the signal supplied from theOR gate 237, the sector mark detecting window output part 238 closes thesector mark detecting window. The sector mark detecting window outputtedfrom the sector mark detecting window output part 238 is supplied to thesector mark detector 217. In accordance with the sector mark detectingwindow supplied from the sector mark detecting window output part 238,the sector mark detector 217 controls the sector mark detection. Also,in accordance with the sector mark detecting window supplied from thesector mark detecting window output part 238, the timing of the IDdetecting window is controlled as shown in FIG. 19F.

[0145] In the above manner, detecting a groove track ID due to crosstalkat a time of land track scanning can be prevented.

[0146] Since only one ID is set for two sectors in the magneto-opticaldisk 201 of this embodiment, a sector mark should be detected both in adata area on the land and a corresponding data area on the groove. Thesector marks detected from both data areas are then compounded into acompound sector mark. By counting the compound sector marks, a onesector passing pulse is generated. Thus, accurate counting of thesectors can be performed.

[0147]FIGS. 21A to 21F illustrate a process for generating one sectorpassing pulse in the information storage apparatus of the presentinvention. More specifically, FIG. 21A shows a format of a land track,FIG. 21B shows a format of a groove track, FIG. 21C shows a land ID readgate, FIG. 21D shows a land sector mark detecting pulse, FIG. 21E showsa groove sector mark detection pulse, and FIG. 21F shows a compoundsector mark detection pulse.

[0148] A land sector mark is first detected in a header in the landformat shown in FIG. 21A. The land sector mark detection pulse shown inFIG. 21D is then generated. Also, a groove sector mark is detected in aheader in the groove format shown in FIG. 21B, and the groove sectormark detection pulse shown in FIG. 21E is then generated.

[0149] The land mark detection pulse shown in FIG. 21D and the groovesector mark detection pulse shown in FIG. 21E are compounded into thecompound sector mark detection pulse shown in FIG. 21F.

[0150]FIG. 22 is an equivalent circuit for generating a compound sectormark in the information storage apparatus of the present invention.

[0151] The sector mark compounding circuit shown in FIG. 22 comprisesAND gates 239 and 240, a NOT circuit 241, and an OR gate 242. The ANDgate 239 receives the land sector mark detection pulse from the sectormark detector 217 and the ID detecting window generated from the bytecounter 219. The AND gate 239 then determines the AND logic between theland sector mark detection pulse and the ID detecting window. The outputof the AND gate 239 is shown in FIG. 21D.

[0152] The AND gate 240 receives the groove sector mark detection pulsefrom the sector mark detector 217 and the ID detecting window generatedfrom the byte counter 219. The AND gate 240 then determines the ANDlogic between the groove sector mark detection pulse and the IDdetecting window. The output of the AND gate 240 is shown in FIG. 21E.

[0153] The outputs of the AND gates 239 and 240 are supplied to the ORgate 242. The OR gate 242 outputs the OR logic between the output of theAND gate 239 and the output of the AND gate 240. The output of the ORgate 242 is shown in FIG. 21F.

[0154] In the above manner, a pulse is outputted in every data area,i.e., in every sector. The pulse is then supplied as the one sectorpassing pulse to the address counter 220.

[0155] In a case where the sector marks formed on groove tracks areshared with land tracks, as shown in FIG. 13, the sector marks on thetwo groove tracks Tr1 and Tr3 are detected with the right and left sideends of the light beam L, which is scanning the land track Tr2.Accordingly, delay is caused, compared with a case where a sector markis detected with the center of the light beam L. In the magneto-opticaldisk 201 of this embodiment, only one ID is set for two data areas.Therefore, it is important to obtain the accurate number of sectors todetermine the address of a data area with no ID. Accordingly, the pulsewidth of the sector mark detection pulse needs to be corrected.

[0156]FIG. 23 is a block diagram of a sector mark detection pulsecorrection circuit of the information storage apparatus in accordancewith the present invention.

[0157] The sector mark detection pulse correction circuit 243 isconnected to the output terminal of the sector mark compounding circuitshown in FIG. 22, for instance. The sector mark detection pulsecorrection circuit 243 comprises a delay circuit 244, an AND gate 245,and an OR gate 246.

[0158] The delay circuit 244 receives the output of the sector markcompounding circuit, i.e., the signal shown in FIG. 21F, and delays thereceived signal by a predetermined time. The delay time is determinedbased on the delay distance T from the center end of the light beam L tothe point where the sector mark on the groove track crosses theperipheral end of the light beam L, as shown in FIG. 13.

[0159] The output of the delay circuit 244 is supplied to the AND gate245. The AND gate 245 also receives a land tracking signal from thecontroller 225, which is high at a time of land track scanning. The ANDgate 245 then outputs the AND logic between the output of the delaycircuit 244 and the land tracking signal. Thus, the output of the delaycircuit 244 can be controlled in accordance with the land trackingsignal.

[0160] The output of the AND gate 245 is supplied to the OR gate 246.The OR gate 246 also receives the output of the sector mark compoundingcircuit, i.e., the signal shown in FIG. 21F. The OR gate 246 thenoutputs the OR logic between the output of the AND gate 245 and theoutput of the sector mark compounding circuit.

[0161] In the above manner, the sector mark detection pulse correctioncircuit 243 makes the pulse width of the sector mark detection pulse atthe time of land track scanning equal to the pulse width of the sectormark detection pulse at the time of groove track scanning. Thus, in thecase where the sector marks on the groove tracks are shared with theland tracks, as shown in FIG. 13, accurate sector mark detection can beperformed.

[0162]FIG. 24 is a block diagram of the gate pulse generator of theinformation storage apparatus in accordance with the present invention.

[0163] The gate pulse generator 224 comprises flip-flops 247 to 251,multiplexers 252 and 253, and an AND gate 254.

[0164] Each of the flip-flops 247-to 251 has a J-K flip-flop function.

[0165] In the flip-flop 248, the land sector mark search start pulse issupplied from the controller 225 to the J input terminal. The K inputterminal is fixed at “0”. The land sector mark detection pulse issupplied from the sector mark detector 217 to the R input terminal. Theflip-flop 248 outputs a land sector mark search pulse.

[0166] In the flip-flop. 249, the groove sector mark search start pulseis supplied from the controller 225 to the J input terminal. The K inputterminal is fixed at “0”. The groove sector mark detection pulse issupplied from the sector mark detector 217 to the R input terminal. Theflip-flop 249 outputs a groove sector mark search pulse.

[0167] In the flip-flop 247, a land/groove identifying pulse is suppliedfrom the byte counter 219 to the J and K input terminals. The output ofthe flip-flop 248 is supplied to the P input terminal, and the output ofthe flip-flop 249 is supplied to the R input terminal. The flip-flop 247then generates a land ID gate pulse. The land ID gate pulse is suppliedto the multiplexers 252 and 253, and the AND gate 254.

[0168] In the flip-flop 250, an ID read gate open pulse is supplied fromthe byte counter 219 to the J input terminal, and an ID read gate closepulse is supplied from the byte counter 219 to the K input terminal. Theflip-flop 250 then generates an ID read gate pulse based on the ID readgate open pulse and the ID read gate close pulse supplied from the bytecounter 219.

[0169] The output of the flip-flop 250 is supplied to the AND gate 254.The AND gate 254 outputs the AND logic between the output of theflip-flop 247 and the output of the flip-flop 250. The flip-flop 250outputs only the land ID read gate pulse of the ID read gate pulse.

[0170] The multiplexer 252 receives first and second synchronizingsignal window open pulses from the byte counter 219. In accordance withthe land ID gate pulse supplied from the flip-flop 247, the multiplexer252 selectively supplies either the first synchronizing signal windowopen pulse or the second synchronizing signal window open pulse to theflip-flop 251. More specifically, when the land ID gate pulse suppliedfrom the flip-flop 247 is high, the multiplexer 252 selects the firstsynchronizing signal window open pulse, and when the land ID gate pulseis low, the multiplexer 252 selects the second synchronizing signalwindow open pulse.

[0171] The multiplexer 253 receives first and second synchronizingsignal window close pulse from the byte counter 219. In accordance withthe land ID gate pulse supplied from the flip-flop 247, the multiplexer253 selectively supplies either the first synchronizing signal windowclose pulse or the second synchronizing signal window close pulse to theflip-flop 251. More specifically, when the land ID gate pulse suppliedfrom the flip-flop 247 is high, the multiplexer 253 selects the firstsynchronizing signal window close pulse, and when the land ID gate pulseis low, the multiplexer 253 selects the second synchronizing signalwindow close pulse.

[0172] In the flip-flop 251, the selective output of the multiplexer 252is supplied to the J input terminal, while the selective output of themultiplexer 253 is supplied to the K input terminal. The flip-flop 251then outputs a synchronizing signal window. When the land ID gate pulseis high, the synchronizing signal window becomes high with the firstsynchronizing signal window open pulse, and becomes low with the firstsynchronizing signal window close pulse. When the land ID gate pulse islow, the synchronizing signal window becomes high with the secondsynchronizing signal window open pulse, and becomes low with the secondsynchronizing signal window close pulse.

[0173]FIGS. 25A to 25M show an operation of the gate pulse generator ofthe information storage apparatus in accordance with the presentinvention. More specifically, FIG. 25A shows a track format, FIG. 25Bshows the land sector mark search start pulse, FIG. 25C shows the landsector mark detection pulse, FIG. 25D shows the groove sector markdetection pulse, FIG. 25E shows the land/groove identifying pulse, FIG.25F shows the land ID gate, FIG. 25G shows the land ID read gate, FIG.25H shows the ID read gate, FIG. 25I shows the first synchronizingsignal window open pulse, FIG. 25J shows the second synchronizing signalwindow open pulse, FIG. 25K shows the first synchronizing signal windowclose pulse, FIG. 25L shows the second synchronizing signal window closepulse, and FIG. 25M shows the synchronizing signal window. It should benoted that the reference numerals used in these figures indicate thesame components as the reference numerals used in FIG. 11.

[0174] When a read/write command is issued, the land sector mark searchstart pulse is outputted as an event, as shown in FIG. 25B. As the landsector mark search start pulse is outputted, the land ID gate is openedas shown in FIG. 25F. After the land ID gate is opened, the land sectormark 124 is supplied, and is then detected as shown in FIG. 25C. Whilethe land ID gate is open, the land ID read gate shown in FIG. 25G isopened. The land ID read gate is opened in the positions of theconventional headers.

[0175] Next, the land/groove identifying pulse shown in FIG. 25E isgenerated as an event, and the land ID gate shown in FIG. 25F is closed.

[0176] When the second synchronizing signal window open pulse shown inFIG. 25J is generated as an event, the synchronizing signal window shownin FIG. 25M is opened. When the second synchronizing signal window closepulse shown in FIG. 25L is generated as an event, the synchronizingsignal window shown in FIG. 25M is closed.

[0177] When the light beam L reaches the sector mark 126, the land IDread gate is opened as shown in FIG. 25G. However, the land ID gateremains closed as shown in FIG. 25F, and accordingly, the ID read gatealso remains closed as shown in FIG. 25H. Thus, groove ID readout can beprevented at the time of land track scanning.

[0178] In the above manner, in a sector without an ID, the servo windowis expanded from 5 bytes to 8 bytes, for instance, so as to provide amargin to hold servo information within the servo window. Thus, servotiming gaps due to irregular disk rotation or disk eccentricity can beabsorbed.

[0179]FIGS. 26A to 26D illustrate the read/write timing operation in adata area of the information storage apparatus in accordance with thepresent invention. More specifically, FIG. 26A shows a format of a trackto be read or written, FIGS. 26B and 26D each show the read/write timingfor the first data area 103-1 or 105-1, and FIG. 26C shows theread/write timing for the second data area 103-2 or 105-2. The referencenumerals in these figures indicate the same components as those in FIG.6.

[0180] In a case where a data read/write operation is performed on thefirst data area 103-1 or 105-1 and the second data area 103-2 or 105-2,the data read/write operation is accepted when the header 102 or 104 isdetected, as shown in FIGS. 26B and 26C. The data read/write operationon the data area having the next ID is performed when the next header102 or 104 is detected. In this manner, the servo error detectionsensitivity can be increased by 20%, compared with the conventionalservo error detection sensitivity.

[0181]FIGS. 27A to 27C illustrate the states of the servo errordetection sensitivity of the information storage apparatus in accordancewith the present invention. More specifically, FIG. 27A is a format of atrack to be scanned with the light beam L, FIG. 27B shows the states ofthe servo error detection sensitivity set by the servo error detectingcircuit 211, and 27C shows the states of the read/write gate.

[0182] When the light beam reaches the data area 103-1 or 105-1 shown inFIG. 27A, the servo error detection sensitivity is increased as shown inFIG. 27B.

[0183] If the light beam drifts from the track of the first data area103-1 to 105-1 to an adjacent track before a read/write operation isperformed on the second data area 103-2 or 105-2, the read/writeoperation might be performed on a data area on the adjacent track.Therefore, the servo error detection sensitivity is increased to detectthe servo error, so that the read/write operation in the wrong positioncan be immediately stopped.

[0184] Although one header is set for two data areas in the aboveembodiment, it is possible to set one header for more than two dataareas. Also, the headers may be arranged in different manners from theabove embodiment.

[0185]FIG. 28 shows a format in a fifth embodiment of the recordingmedium in accordance with the present invention. As shown in FIG. 28,one header is set for four data areas, and each header is shifted fromthe headers on the adjacent tracks.

[0186]FIG. 29 shows a format in a sixth embodiment of the recordingmedium in accordance with the present invention. In this embodiment, asector mark is placed before each data area without an ID, and the otherarrangements are the same as in FIG. 28.

[0187] With the recording medium or the information storage apparatus ofthis embodiment, the formatting efficiency is increased from 87% to 93%.Since a sector mark is provided for each data area without an ID, aread/write gate deviation due to disk eccentricity or rotation jittercan be corrected.

[0188] As described so far, since the ID read gate for reading an ID isnot outputted in a data area without an ID, an ID on an adjacent trackcannot be read when crosstalk occurs in the data area without an ID.Thus, wrong ID detection can be prevented.

[0189] Moreover, in a land/groove medium having close-pitched tracks asshown in FIG. 13, the sector marks on the groove tracks can be detectedby crosstalk when the light beam is scanning a land track. Thus, sectormark detection can be accurately performed without forming a sector markon the land tracks.

[0190] Also, in a land/groove medium, the sector marks on the landtracks and the sector marks on the groove tracks may be differentiatedas the “EVEN BAND” and the “ODD BAND” specified in ISO/IEC 15041. Bydoing so, at a time of land track scanning, the ID read gate is openedonly when a sector mark on the land track is detected. Thus, groove IDreading can be prevented at the time of land track scanning. In the casewhere-the “EVEN BAND”and “ODD BAND” specified in ISO/IEC 15041 areemployed, the sector mark detector is unnecessary. For instance, sectormark detection can be performed by a sector mark detector in a 640-Mbytemedium that is already on the market, and compatibility with theexisting 640-Mvyte media can be maintained.

[0191] The present invention is not limited to the specificallydisclosed embodiments, but variations and modifications may be madewithout departing from the scope of the present invention.

[0192] The present application is based on Japanese priority applicationNo. 11-192311, filed on Jul. 6, 1999, the entire contents of which arehereby incorporated by reference.

What is claimed is:
 1. A recording medium comprising: data sectors; and identifier portions each provided for more than one of the data sectors, each of the identifier portions being arranged in positions shifted from the identifier portions on adjacent tracks.
 2. The recording medium as claimed in claim 1, wherein predetermined tracks are produced in the form of lands, and other tracks adjacent to the predetermined tracks are produced in the form of grooves.
 3. The recording medium as claimed in claim 1, wherein the identifier portions have addresses which are consecutive in a direction of the tracks.
 4. The recording medium as claimed in claim 1, wherein the identifier portions have addresses which are consecutive in a direction of the tracks at intervals of a constant address value.
 5. The recording medium as claimed in claim 1, wherein synchronizing information portions for distinguishing the data sectors are provided between the data sectors.
 6. The recording medium as claimed in claim 5, wherein the synchronizing information portions are arranged adjacent to each other on mutually adjacent tracks.
 7. The recording medium as claimed in claim 5, wherein the synchronizing information portions between sectors on adjacent tracks have the same pattern, and the pattern of the synchronizing information portions in the data sectors with the identifier portions on a track are different from the pattern of the synchronizing information portions in the data sectors with no identifier portions.
 8. The recording medium as claimed in claim 6, wherein the synchronizing information portions are provided on every other track.
 9. An information storage apparatus for making access to a recording medium which has data sectors, and identifier portions each provided for more than one of the data sectors, each of the identifier portions being arranged in positions shifted from each other on adjacent tracks, said information storage apparatus comprising: an address determination unit which generates addresses of the data sectors based on the identifier portions, and determines whether a desired data sector is reached in accordance with the addresses.
 10. The information storage apparatus as claimed in claim 9, wherein the address determination unit counts the number of data sectors, and generates the addresses based on the identifier portions and the number of the data sectors.
 11. The information storage apparatus as claimed in claim 9, further comprising a servo controller which changes servo error sensitivity based on an identifier portion closest to a desired data sector having no identifier portion when read/write is performed on the desired data sector.
 12. The information storage apparatus as claimed in claim 9, wherein the address determination unit outputs a window signal having an expanded margin with respect to timing at which the address determination unit determines the address of a data sector with no identifier portion.
 13. The information storage apparatus as claimed in claim 9, wherein when the address determination unit determines the address of a data sector with no identifier portion, data is received from a data sector which has the identifier portion and is located immediately before the sector with no identifier portion. 